Bending method and device therefor

ABSTRACT

At a time of executing a bending process of a work according to a cooperation between a punch and a die, a provisional stroke value for obtaining a predetermined angle is determined on the basis of a bending process condition. A test bending process is executed on the basis of the provisional stroke value, and a striking number required for striking the work until the predetermined angle is obtained is judged. Since a stroke value correction amount at a time of a main bending corresponding to the striking number and the predetermined angle is previously determined, a main bending process is executed by correcting to a stroke value at a time of the main bending by computing the corresponding stroke value correction amount on the basis of the stroke value correction amount at a time of the main bending process.

TECHNICAL FIELD

[0001] The present invention relates to a bending method in a bending apparatus, and an apparatus thereof.

BACKGROUND ART

[0002] Conventionally, in a bending apparatus, for example, a press brake, a plate-like work is bent so as to have a desired predetermined angle according to a cooperation of a punch and a die.

[0003] Generally, at a time of bending, at first, a D value (a stroke amount) for obtaining a predetermined angle on the basis of “test bending” is detected.

[0004] This “test bending” means a step of switching an NC control apparatus to a manual mode and thereafter driving a ram at a minute speed by a manual pulser which is executed by rotating a manual pulse handle by an operator to bend a work.

[0005] After the D value (the stroke amount) at a time when the predetermined angle, for example, 90 degrees is established in the test bending step mentioned above is determined, the D value is set to the NC control apparatus, whereby a continuous bending (a step of continuously bending a plurality of works) is executed as a “main bending”.

[0006] However, in the conventional bending method, there is a problem that since the D value with respect to the predetermined angle which is determined at a time of test bending is set to the NC control apparatus, the work does not obtain the predetermined angle even if the D value is used in the main bending operation as it is and the continuous bending process is executed, so that the angle becomes shallower or deeper.

DISCLOSURE OF THE INVENTION

[0007] The present invention has been made for the purpose of solving the problem mentioned above. Accordingly, an object of the present invention is to provide a bending method and an apparatus thereof which can determine a D value correction amount at a time of main bending on the basis of a striking number until a predetermined angle is established at a time of test bending so as to easily conduct bending at the predetermined angle.

[0008] In order to achieve the object mentioned above, according to a first aspect of the present invention, there is provided a bending method comprising the steps of: determining a provisional stroke value for obtaining a predetermined angle on the basis of a bending process condition; reciprocating any one of an upper table and a lower table on the basis of the provisional stroke value so as to execute a test bending process of a work according to a cooperation of a punch and a die which are attached to the upper table and the lower table; striking the work at a predetermined number until the predetermined angle is obtained, thereby previously determining a stroke value correction amount at a time of main bending in correspondence to the striking number and the predetermined angle; calculating the corresponding stroke value correction amount on the basis of the predetermined number before the main bending process; and adding the stroke value correction amount to the provisional stroke value so as to correct to a stroke value at a time of the main bending, thereby executing the main bending process.

[0009] According to a second aspect of the present invention, there is provided a bending apparatus comprising: an upper table and a lower table, one of them being capable of reciprocating; a punch and a die which are attached to the upper table and the lower table; working condition inputting means for inputting a bending process condition; provisional stroke value determining means for determining a provisional stroke value by the bending process condition inputting means; striking number judging means for inputting or automatically detecting a striking number at which a work has been struck until a predetermined angle is obtained, by executing a bending process according to a cooperation of the punch and the die at a time of a test bending, on the basis of the provisional stroke value computed by the provisional stroke value determining means; and stroke value correction amount computing means for computing a stroke value correction amount with respect to a predetermined angle at a time of the main bending on the basis of the striking number which has been judged by the striking number judging means.

[0010] Therefore, according to the bending method and the apparatus thereof which are based on the inventions of the first and second aspects, the corresponding stroke value correction amount can be automatically computed on the basis of a data base of the stroke value correction amount corresponding to the predetermined angle, the striking number and the bending process condition at a time of the main bending process, by previously determining the data base mentioned above and striking at the predetermined number so that the predetermined angle is obtained at a time of the test bending.

[0011] That is, the main bending process is executed on the basis of the main bending stroke value which is automatically corrected by adding the stroke value correction amount to the provisional stroke value. As a result, even when the test bending is executed by the operator who is not a skilled operator and plural number of striking operations are executed until the desired predetermined angle is obtained, it is possible to easily and effectively execute a stable bending process.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a flow chart of a bending method, which shows an embodiment according to the present invention;

[0013]FIG. 2 is a flow chart of an improved bending method, which shows an embodiment according to the present invention;

[0014]FIG. 3 is a schematic front elevational view of a press brake used in an embodiment according to the present invention;

[0015]FIG. 4 is a block diagram of a control apparatus;

[0016]FIG. 5 is a correction value table showing a part of a plural number striking correction data base, which shows an embodiment according to the present invention;

[0017]FIG. 6 is an explanatory schematic view explaining a D value correction amount at a time of a main bending with respect to a twice striking, which shows an embodiment according to the present invention; and

[0018]FIG. 7 is a graph showing an influence of the twice striking to an angle.

BEST MODE FOR CARRYING OUT THE INVENTION

[0019] A description will be given in detail below of an embodiment according to this invention with reference to the accompanying drawings.

[0020] According to a bending method of the present invention, as shown in FIG. 1, a test bending process is executed after an elongation value at a time of a bending process is computed. If a bending angle is a predetermined angle, the step goes to a continuous bending process (steps S101 to S103 and S108).

[0021] In the case that an operator who is not a skilled operator executes the test bending mentioned above, in order to obtain a desired predetermined angle, there are repeated at two or three times steps (steps S104 to S106) of taking out a work after bending once so as to measure a bending angle of the work, again mounting the bent work on a die, rotating a manual pulser so as to execute a striking by a punch and the die, and driving a ram so as to drive in the bending angle.

[0022] After a D value (a stroke amount) at a time when the predetermined angle, for example, 90 degrees is established in the test bending step mentioned above is determined, the D value is set to an NC control apparatus, whereby a continuous bending (a step of continuously bending a plurality of works) is executed as a “main bending” (steps S107 and 108).

[0023] In the bending method mentioned above, there has been a problem that, even if the D value with respect to the predetermined angle which is determined at a time of the test bending is set to the NC control apparatus, the D value is used in the main bending operation as it is and the continuous bending process is executed, the work does not become the predetermined angle, and the angle becomes shallower or deeper. According to a general tendency, it becomes a tighter angle (a narrower angle) than the predetermined angle.

[0024] Further, when a target angle correction is executed by once releasing the work from a press brake for the purpose of measuring a spring back by using an automatic angle correcting apparatus such as a bending indicator (B/I: a bending angle measuring apparatus) or the like and again gripping the work between the punch and the die, and the continuous bending process is executed on the basis of the D value at this time, the angle becomes shallower or deeper in the same manner as that mentioned above.

[0025] Then, the applicant of the present invention has improved the invention mentioned above. A description will be given in detail below of an embodiment of a bending method and an apparatus thereof according to the improved invention with reference to FIGS. 2 to 7 by employing a hydraulic type press brake for an example of the press brake.

[0026] With reference to FIG. 3, a press brake 1 according to the present embodiment aims at a descending type hydraulic press brake, but it may be an ascending type press brake or a mechanical type press brake which is not a hydraulic type but is of a crank type or the like.

[0027] The descending type hydraulic brake 1 is attached and fixed to a lower surface of a movable table capable of moving upward and downward, that is, for example, an upper table 5 corresponding to a ram via a plurality of intermediate plates 3 in which punches P are arranged at a uniform interval. A die D is attached and fixed to an upper surface of a fixed table, for example, a lower table 7. Accordingly, the upper table 5 moves downward, and a bending process of a work W constituted by a plate member is executed between the punch P and the die D according to a cooperation between the punch P and the die D.

[0028] In upper portions of left and right side frames 9 and 11 in FIG. 3 which constitute a main body frame, left shaft(axis) and right shaft (axis) hydraulic cylinders 13 and 15 are provided, and a structure is made such that the upper table 5 is connected to lower ends of piston rods 17 of the left shaft and right shaft hydraulic cylinders 13 and 15.

[0029] Further, the lower table 7 is fixed to lower portions of the left and right side frames 9 and 11, notch portions 19 are provided in a center portion of the lower table 7, and two crowning apparatuses, for example, crowning cylinders 21 and 23 (hydraulic cylinders) are provided in the notch portions 19. A structure is made such that an applied pressure of pistons in the crowning cylinders 21 and 23 is controlled, whereby an amount of deflection in the center portion of the lower table 7 is adjusted.

[0030] Further, a control apparatus 25 such as an NC control apparatus or the like is provided in the press brake 1 mentioned above, and this control apparatus 25 is structured such as to be switched between a “test bending mode” for manually executing a bending process by rotating a manual pulse handle (not shown) at a time of executing a “test bending” so as to drive the upper table 5 at a minute speed by a manual pulser, and a “continuous bending mode” for executing a continuous bending process corresponding to a so-called “main bending” which continuously bends a plurality of works W after a D value (a stroke amount) at a time when a predetermined angle is achieved by this test bending is reflected to the control apparatus 25.

[0031] With reference to FIG. 4, in the control apparatus 25, a bending process condition inputting means for inputting data such as a material of work W, a thickness, a worked shape, a metal mold condition, a target angle of bending and a working program in the work W, and the like, for example, an input apparatus 29 and a display apparatus 31, and a memory 33 storing the input data are electrically connected to a CPU 27 corresponding to a central processing unit.

[0032] Further, to the CPU 27 mentioned above, there are electrically connected a provisional D value determining portion 35 corresponding to a provisional stroke value determining means for determining a provisional D value (stroke amount) by means of the input apparatus 29, a striking(bending) number judging means for inputting or automatically detecting a striking(bending) number at a time of striking the work W until the predetermined angle is obtained by the bending process according to the provisional D value computed by the provisional D value determining portion 35, for example, a striking number judging portion 37, a stroke value correction amount computing means for computing a D value correction amount at a time of a main bending with respect to the predetermined angle on the basis of the striking number by the striking number judging portion 37, for example, a D value correction amount computing portion 39, and a main bending command portion 41 which gives a command so that the main bending process is executed according to the main bending D value corrected on the basis of the D value correction amount computed by the D value correction amount computing portion 39.

[0033] On the basis of the structure mentioned above, a description will be given with reference to a flow chart in FIG. 2. For example, data of the material, the thickness, the bending length and the bending position of the work W, a metal mold condition such as a V width of the die, a step diameter DR of the die, a radius PR of a punch front end and the like, a predetermined angle and an actually measured angle corresponding to a target angle of bending, and the like are input as the bending process condition, by the input apparatus 29 of the control apparatus 25 (a step S1).

[0034] The D value is calculated by the provisional D value determining portion 35 of the control apparatus 25 on the basis of the input data mentioned above. The D value becomes the provisional D value at a time of the test bending (a step S2).

[0035] The test bending process is executed by the provisional D value mentioned above. That is, after the control apparatus 25 is switched to the test bending mode and the work W is mounted on the die D, the manual pulser is rotated by the operator, the upper table 5 is driven at a minute speed, and the work W is bent. At this time, since the work becomes defective if the bending angle becomes tighter than the predetermined angle (more acute than the predetermined angle), the provisional D value is actually set so as to be always 1 degree to 2 degrees slacker than the predetermined angle. Then, the test bending is executed on the basis of the provisional D value, and the bending angle of the work W is driven in.

[0036] That is, the operator drives in so as to be close to the predetermined angle while again rotating the manual pulser after again setting the work W on the die D at a time when the operator takes out the work W and measures the bending angle, and the predetermined angle is not obtained (steps S3 to S7).

[0037] The matter how many times the work is struck until the predetermined angle within an allowable value is finally obtained, that is, the striking(bending) number is input to the control apparatus 25. The striking number may be manually input by the operator by means of the input apparatus 29, or may be automatically input by being automatically counted, for example, by a counter installed within the control apparatus 25. The striking number to be input is obtained, for example, by a number at a time when the upper table 5 stops being counted by the control apparatus 25.

[0038] For example, on the assumption that the target angle is 90 degrees at a time of the test bending, the operator rotates the manual pulser so as to driven in the angle after the operator pedals a foot pedal and the upper table 5 is automatically moved downward and stops until the bending angle becomes at first 92 degrees. Accordingly, the number at which the upper table 5 stops at a descending end by pedaling the foot pedal is counted by the operator, or the number detected by the striking number detecting apparatus such as the detection sensor or the like is automatically counted, for example, by the counter. According to the manual or automatic manner mentioned above, the striking number is judged by the striking number judging portion 37 of the control apparatus 25 (a step S8).

[0039] Further, as mentioned above, the D value at a time when the predetermined angle is obtained by the test bending is registered in the memory 33 of the control apparatus 25 (a step S9).

[0040] With reference to FIG. 5, on the basis of the data obtained by previously executing the test bending process, there can be prepared a D value correction amount corresponding to the striking number until the target angle is obtained. That is, a plural number striking correction database (a correction value table) is obtained.

[0041] For example, in the table shown in FIG. 5, a material of the work W is SUS304, a thickness thereof is 1.2 mm, an angle of the punch front end is 88 degrees, a V width of the die D is 6 mm, a step radius DR of the die D is 1.5 mm, and a radius PR of the punch front end is 0.6 mm. Under this condition, the test bending is executed with respect to each of the target angles 90 degrees, 100 degrees, 110 degrees, 120 degrees, 130 degrees and 140 degrees. The D value correction amount corresponding to the striking number (twice striking to six times striking in the table) executed until each of the target angles is obtained is described.

[0042] Describing in more detail, the D value correction amount at a time when the target angle is 90 degrees and the striking number is twice is 0.011 mm. This shows that the descending end of the punch P at a time when the twice striking is executed until the target angle becomes 90 degrees is at a position shown by a two-dot chain line as shown in FIG. 6, however, it is necessary that the descending end of the punch P further moves downward to a position shown by a solid line in FIG. 6, for example, at 0.011 mm, in order that the target angle becomes 90 degrees according to the main bending (single striking).

[0043] With reference to FIG. 7, this drawing shows results at a time when the work is bent in a breath on the basis of the same D value and at a time when the work is bent until the bending angle becomes close to 100 degrees, is then released once, is again gripped between the punch P and the die D, and is bent on the basis of the same D value. As is known from a graph in FIG. 7, in the case that the twice striking is executed at the same stroke amount (D value) as the D value at a time when for example, the bending angle of 90 degrees (position of θ 2 in FIG. 7) is obtained according to the normal bending (once striking), an actually measured value of the bending angle according to the twice striking becomes an angle a deeper (more acute) than that at the normal bending time.

[0044] In another respect, since the bending angle of 90 degrees is not obtained even when the twice striking is executed at the test bending time and the main bending (once striking) is executed at the same stroke amount as the D value at a time when the bending angle of 90 degrees is obtained, it is necessary that the main bending is executed by setting the stroke amount to the D value correction amount 5 mm which is deeper (additive) with respect to the D value at the twice striking time. The D value correction amount 5 mm corresponds to 0.011 mm in FIG. 5.

[0045] Next, the main bending process (the continuous bending process) is executed. At this time, the control apparatus 25 is switched to the continuous bending mode. On the basis of the striking number input by the operator in the step S8 or the automatically detected striking number, the D value correction amount corresponding to the target angle and the striking number is computed by the D value correction amount computing portion 39 of the control apparatus 25 on the basis of the plural number striking correction data base within the memory 33.

[0046] For example, on the assumption that the striking number at the test bending time mentioned above is two, the D value correction amount at the twice striking time with respect to the target angle is computed by the D value correction amount computing portion 39 of the control apparatus 25, on the basis of the twice data of the striking number which is input by the operator by means of the input apparatus 29 or is automatically counted, the bending process condition, and the plural time striking correction data base within the memory 33. The D value at the test bending time which is registered in the step S9 is corrected by the D value correction amount, and the main bending D value (the stroke amount) at the main bending time is computed.

[0047] In this case, since the plural time striking correction data base mentioned above can be expressed by a computation formula (an experimental formula) D value correction amount=f (material, thickness, target angle, metal mold data and striking number) as is known from the graph in FIG. 6, the D value correction amount may be computed on the basis of the computation formula (a step S10).

[0048] The main bending process of a predetermined number of works W is executed according to the main bending D value corrected on the basis of the D value correction amount, by the command given from the main bending command portion 41 of the control apparatus 25 (steps S11 to S12).

[0049] Since the D value correction amount corresponding to the bending process condition executed at the main bending time is previously determined on the basis of the predetermined angle and the striking number at the test bending time, and the bending process condition as mentioned above, and the D value correction amount is made in the form of the computation formula (the experimental formula) or in the form of the data base at each of the bending process conditions, the main bending process is executed according to the main bending D value which is automatically corrected by the D value correction amount on the basis of the computation formula mentioned above or the data base. Accordingly, even when the test bending is executed by the operator who is not the skilled operator and the plural number of striking is executed until the desired predetermined angle is obtained, it is possible to easily and effectively execute the stable bending process.

[0050] In this case, this invention is not limited to the embodiment mentioned above, and can be carried out on the basis of the other aspects by executing a proper modification. 

1. A bending method comprising the steps of: determining a provisional stroke value for obtaining a predetermined angle on the basis of a bending process condition; reciprocating any one of an upper table and a lower table on the basis of the provisional stroke value so as to execute a test bending process of a work according to a cooperation of a punch and a die which are attached to the upper table and the lower table; striking the work at a predetermined number until the predetermined angle is obtained, thereby previously determining a stroke value correction amount at a time of main bending in correspondence to the striking number and the predetermined angle; calculating a corresponding stroke value correction amount on the basis of the predetermined number before the main bending process; and adding the stroke value correction amount to the provisional stroke value so as to correct to a stroke value at a time of the main bending, thereby executing the main bending process.
 2. A bending apparatus comprising: an upper table and a lower table, one of which is capable of reciprocating; a punch and a die which are attached to the upper table and the lower table; working condition inputting device to input a bending process condition; provisional stroke value determining device to determine a provisional stroke value by the bending process condition inputting device; striking number judging device to input or automatically detect a striking number at which a work has been struck until a predetermined angle is obtained, by executing a bending process according to a cooperation of the punch and the die at a time of a test bending, on the basis of the provisional stroke value computed by the provisional stroke value determining device; and stroke value correction amount computing device to compute a stroke value correction amount with respect to a predetermined angle at a time of the main bending on the basis of the striking number which has been judged by the striking number judging device. 